The present invention generally relates to circuits for reducing noise in carrier chrominance signals, and more particularly to a noise reducing circuit capable of effectively eliminating a noise component within a carrier chrominance signal of a color video signal without much loss of an information signal component.
Conventionally, as a circuit for reducing noise in a carrier chrominance signal, there was a noise reducing circuit employing a feedback type comb filter. This comb filter had a filtering characteristic for passing only the chrominance subcarrier frequency 3.58 MHz and frequency components of the side bands thereof, for example. However, when there is no rapid change in the chrominance information of the carrier chrominance signal and the color is constant, the carrier chrominance signal does not have side bands. Thus, if the carrier chrominance signal passed through the above conventional noise reducing circuit is such that the color of the chrominance information of the carrier chrominance signal is constant and the carrier chrominance signal does not have side bands, there are no side bands which pass through the comb filter, however, a noise component within the side bands pass through the comb filter. As a result, the conventional noise reducing circuit suffered a disadvantage in that sufficient noise reduction could not be carried out.